Abstract

A new specimen of the protorosaur Macrocnemus fuyuanensis, from the Zhuganpo Member of the Falang Formation at Fuyuan (Yunnan Province, southwestern China), is described and compared with Macrocnemus bassanii. The new specimen is the first in the genus Macrocnemus that clearly shows details of the preorbital region of the skull. A large, plate-like lacrimal is located in front of the tall, columnar prefrontal that defines the anterior margin of the orbit. A longitudinally oriented nasal groove extends along the anterior two-thirds of the snout, accommodating the external naris at its anterior part. A similar preorbital depression has previously been described for Dinocephalosaurus and it is also reported here for the first time in Tanystropheus. The new specimen confirms the status of Macrocnemus fuyuanensis as a species distinct from Macrocnemus bassanii on the basis of a humerus that significantly exceeds the radius in length. The occurrence of both Macrocnemus and Tanystropheus in southwestern China further underscores the close faunal affinities of the eastern and western Tethyan realms during the Middle and early Late Triassic.